1. Field of the Invention
The present invention relates to touch panels used for operating a range of electronic devices.
2. Background Art
In recent years, a range of electronic devices, including mobile phones and electronic cameras, are becoming more sophisticated and diversified. Electronic devices, in which a light-transmissive touch panel is attached to a front face of a display element such as liquid crystal, have been developed. Diversifying functions of an electronic device is switched over as the user operates a touch panel typically by finger while looking at indication of display element via the touch panel. Therefore, the user demands electronic devices that can be easily and reliably operated. FIG. 5 is a sectional view of conventional touch panel 100. FIG. 6 is an exploded perspective view of conventional touch panel 100. To facilitate understanding of structures in these drawings, dimensions are partially enlarged.
Multiple belt-like light-transmissive upper conductive layers 102 are aligned on a top face of film-like light-transmissive top substrate 101. Upper conductive layers 102 are formed of material such as indium tin oxide. One end of each of multiple upper electrodes 103 is connected to an end of each of upper conductive layers 102. The other end of each of upper electrodes 103 is led out to one peripheral end of top substrate 101. Upper electrodes 103 are typically formed of copper or silver, and are led out in a direction perpendicular to the stretching direction of upper conductive layers 102.
Multiple belt-like light-transmissive lower conductive layers 105 are aligned on a top face of film-like light-transmissive bottom substrate 104 in a direction perpendicular to the stretching direction of upper conductive layers 102. Lower conductive layers 105 are typically formed of indium tin oxide. One end of each of multiple lower electrodes 106 is connected to an end of each of lower conductive layers 105. The other end of each of lower electrodes 106 is led out to one peripheral end of bottom substrate 104. Lower electrodes 106 are typically formed of copper or silver.
Top substrate 101 is overlaid on the top face of bottom substrate 104, and film-like light-transmissive cover sheet 107 is overlaid on the top face of top substrate 101. Cover sheet 107 and top substrate 101 are attached by adhesive layer 108A, and top substrate 101 and bottom substrate 104 are attached by adhesive layer 108B. This configures touch panel 100. Adhesive layers 108A and 108B are typically formed of acryl or rubber.
Touch panel 100 configured in this way is disposed on a front face of display element (not illustrated), such as liquid crystal, and mounted on an electronic device (not illustrated). Multiple upper electrodes 103 and lower electrodes 106 led out to one peripheral end are electrically connected to an electronic circuit (not illustrated) of the electronic device typically via a flexible wiring board and connector (not illustrated).
In the state that voltage is applied from the electronic circuit to upper electrodes 103 and lower electrodes 106, the user operates the electronic device by touching the top face of cover sheet 107 typically by finger, depending on indication of display element on the rear face of touch panel 100. The electronic circuit detects a point of operation by the change in static capacitance between upper conductive layers 102 and lower conductive layers 105 at a point where the user has operated, and switches diversifying functions of the electronic device.
For example, in the state that multiple menus are displayed by the display element on the rear face, the user touches the top face of cover sheet 107, typically by finger, to select a desired menu. This operation makes a part of potential move to the finger, and changes capacitance between upper conductive layers 102 and lower conductive layers 105 at a point where touch panel 100 has been operated. The electronic circuit detects this change, and thus the desired menu is selected.